• Julian Fürmetz, Sven Patzler, Galina Cosola, Florian Wolf, Nikolaus Degen, Wolf Christian Prall, Christian Ehrnthaller, Wolfgang Böcker, and Peter Helmut Thaller.
• 3D-Surgery, Department of General, Trauma and Reconstructive Surgery, Munich University Hospital LMU, Nußbaumstr. 20, 80336, München, Germany; Department of Sports Traumatology and Arthroscopic Surgery, BG Trauma Center Murnau, Murnau, Germany. Electronic address: julian.fuermetz@bgu-murnau.de.
• Injury. 2022 Oct 1; 53 (10): 3502-3507.

ObjectiveWhile long standing radiographs (LSR) represent the gold standard for preoperative alignment assessment and planning of lower limb deformity corrections, there is no consensus about the intraoperative alignment assesments (IAC) due to various limitations of the common methods. The present study introduces a radiolucent X-ray grid with integrated radiopaque lines explicitly designed for fluoroscopic IAC and evaluates its reliability in comparsion to the LSR.MethodsPatients with posttaumatic and congenital lower limb deformity surgery and preoperative LSR as well as fluoroscopic IAC utilizing the X-ray grid were retrospectively included to the study. The mechanical axis deviation (MAD) in percentage of the maximum tibial width from the medial to the lateral in comparison between the image pairs was set as primary outcome parameter. Multiple rater and measurements determined intra- and interobserver reliabilit of both imaging methods. In addition, the effects of age, gender, body mass index (BMI), etiology, joint line convergence angle (JLCA), and extent varus or valgus deformity were analysed.ResultsA total of 84 patients were finally included. The mean absolute difference of MAD between the two techniques was 7.2 ± 0.8%. MAD between the LSR and IAC correlated at a high level (R = 0.96, p <0.001). The agreement decreased with increasing extent of deformity (p <0.01) and with higher deviation of JLCA between LSR and IAC (p <0.01). Intra- and interobserver concordance correlation coefficient (CCC) for MAD measurements were 0.99 for both imaging techniques.ConclusionFluoroscopy combined with the X-ray grid method is a valid tool for intraoperative assessment of lower limb alignment in deformity correction surgery, and the correlation between LSR and IAC is better than in other similar techniques described in the literature. However, in case of severe coronal alignment deformity and highly divergent JLCA, the agreement between both imaging techniques decreases significantly.Copyright © 2022. Published by Elsevier Ltd.

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